The disclosure herein relates generally to electronic devices, and more particularly to digital camera modules. Even more particularly, it relates to a digital camera module design that prevents or minimizes debris and particulate matter produced by the focusing process from contaminating the sensor array of an image capture device.
Digital camera modules are currently being incorporated into a variety of electronic devices. Such camera hosting devices include, but are not limited to, cellular telephones, personal data assistants (PDAs), and computers. The demand for digital camera modules continues to grow as the ability to incorporate the camera modules into host devices expands. Therefore, one design goal of digital camera modules is to make them as small as possible so that they will fit into an electronic device without substantially increasing the overall size of the device. Means for achieving this goal must, of course, preserve the quality of the image captured by the camera modules.
Such digital camera modules typically include a substrate, an image capture device, a housing, and a lens unit. The substrate is typically a printed circuit board (PCB) that includes circuitry to facilitate data exchange between the image capture device and the host device. The image capture device is mounted and electrically coupled to the circuitry of the PCB. The housing is then mounted on the PCB over the image capture device. The housing includes an opening that receives and centers the lens unit with respect to the image capture device. Typically, the opening includes a set of threads and the lens unit includes a complementary set of threads that facilitate the factory focusing of the camera module. During a factory focus operation, for example, focusing equipment rotates the lens unit with respect to the housing, which adjusts the distance between the lens unit and the image capture device. When the lens unit is properly focused, it is fixed in position with respect to the housing with an adhesive, a thermal weld, or the like.
Camera modules that are focused via thread sets have some disadvantages. For example, as the lens unit is rotated within the housing, sliding friction between threads can create particulate debris that could easily contaminate the image sensor and/or other optical components (e.g., infra-red filters, protective covers, other lenses, etc.). Consequently, these contaminants can accumulate and noticeably degrade the quality of captured images by, for example, blocking light to the image sensor. As another example, focusing operations can be difficult and consume a great deal of manufacturing time. As a result, the manufacturing output rate of camera modules that are focused via threads is relatively low.
In efforts to minimize the accumulation of such debris, manufacturers currently have to closely control the amount of torque used to rotate the lens unit during factory focusing. However, doing so is tedious and still can cause a significant amount of debris to form. Oftentimes, camera modules have to be discarded as a result of being contaminated. Accordingly, there are relatively high yield losses associated with camera modules that are focused via threads.
What is needed, therefore, is a camera module design that is less susceptible to contamination during the assembly and focusing processes. What is also needed is a camera module design that improves manufacturing output and focal accuracy.